1. Field of the Invention
This disclosure relates generally to improvements of various components and systems commonly found in bent-axis pump/motors.
2. Description of the Related Art
Bent-axis pump/motors provide a high degree of efficiency in converting energy supplied as a pressurized fluid, from a hydraulic accumulator, or some other pressurized fluid source, into kinetic energy. Additionally, bent-axis pump/motors provide a further advantage over many other hydraulic technologies, inasmuch as bent-axis pump/motors operate equally well as pumps or motors, providing the potential, in automotive applications, of reclaiming and storing kinetic energy during braking, for use during a subsequent acceleration.
FIG. 1 shows a simplified diagrammatical representation of a hydraulic pump/motor system 100. The system 100 comprises a bent-axis pump/motor 102, which includes a casing 125, a yoke 118 and a cylinder barrel 104.
The cylinder barrel 104 has piston cylinders 106 radially spaced around a common center. The barrel 104 is configured to rotate around an axis A. Each of the cylinders 106 includes a piston 108 having a first end 110 positioned within the cylinder 106, and configured such that there is a pressure tight seal between the first end 110 of the piston 108 and the wall of the respective cylinder 106. A second end 112 of each of the pistons 106 engages a drive plate 114, which is coupled to an input/output shaft 116 of the pump/motor 102.
The angle of the barrel 104 relative to the drive plate 114 dictates the displacement volume of the pump/motor 102 and hence the amount of energy converted by the pump/motor 102.
The angle of the barrel 104 is controlled by the yoke 118, which includes a back plate 119 to which the barrel 104 is rotatably coupled. The yoke 118 further includes a pair of trunnions 120, 121 upon which the yoke 118 rotates, around an axis B. The trunnions 120, 121 are received by apertures 122, 123 in the pump/motor casing 125, and their rotation is accommodated by bearings 126, 127 that are positioned within the apertures 122, 123 of the casing 125, and which encircle the trunnions 120, 122, respectively. As the yoke 118 rotates around axis B, so also does the barrel 104, thereby changing the barrel angle relative to the drive plate 114.
Fluid channels 128, 129 are coupled from the yoke 118, via a valve plate surface 130 of the back plate 119, to each of the cylinders 106 of the barrel 104, as the barrel 104 rotates over the valve plate 130. The fluid channels 128, 129 run down respective arms 132, 133 of the yoke 118 to the trunnions 120, 121. The channels 128, 129 within the yoke 118 terminate at the trunnions 120, 121 at respective ports 134, 135 that are positioned to couple with corresponding fluid ports 136, 137 within the pump/motor casing 125.
The fluid ports 136, 137 of the pump/motor casing 125 are each coupled to low- and high-pressure fluid sources 138, 140, via respective switching valves 142, 143 configured to selectively couple the low-pressure source 138 to one side of the pump/motor 102 via the arm 132 of the yoke 118 and the high-pressure source 140 to the other side of the pump/motor 102 via the other arm 133, or alternatively, to reverse this arrangement. In this way, the device can be selectively configured to apply rotational force to the output shaft 116 in a clockwise or counter-clockwise direction. The coupling between the valves 142, 143 and the fluid ports 136, 137 of the pump/motor casing 125 is generally accomplished using respective pressure hoses 144, 145.
The casing 125 encloses the moving parts of the pump/motor 102. In some systems, the space 117 within the casing 125 is filled with hydraulic fluid and may be in fluid communication with the low-pressure fluid source 138 via a high volume, low loss fluid connection such as a large-bore pressure hose (not shown). This connection maintains the fluid in the casing 125 at a pressure substantially equal to the pressure at the low-pressure fluid source 138. Accordingly, the pump/motor casing 125 may be manufactured to withstand the pressure of the low-pressure fluid source 138. This pressure may be on the order of 100 to 300 psi.
In operation, for example, in an application in which the pump/motor system 100 is coupled to the drive train of a vehicle, fluid from the high-pressure source 140 is coupled to fluid port 137 of the pump/motor 102 by valve 143. The other fluid port 136 is simultaneously coupled to the low-pressure fluid source 138 by the other valve 142. High-pressure fluid enters the pump/motor 124 via the fluid port 137, passes from trunnion 121, through the channel 129, to the valve plate 130 and into the cylinders 106, as the barrel 104 rotates over the valve plate 130. The pistons 108 are sequentially driven against the drive plate 114, causing the drive plate 114 to rotate around a “bent” axis A to achieve displacement. As the barrel 104 also rotates around axis A, the fluid in the cylinders 106 is sequentially released through the valve plate 130 and into the channel 128, to be vented back through the valve 142 to the low-pressure fluid source 138. In this manner, energy from the high-pressure source 140 is converted to kinetic energy by the pump/motor 102 to be transmitted via the rotating shaft 116 to the drive train of the vehicle or other mechanical system.
To slow the vehicle or other mechanical system, the high- and low-pressure connections are reversed, such that the low-pressure source 138 is coupled by the valve 143 to the port 137, while the high-pressure source 140 is coupled by the valve 142 to the port 136. Such a configuration, with the pump/motor 102 at rest, would cause the shaft 116 to rotate in the opposite direction. However, inasmuch as the shaft 116 is coupled to the drive train of the vehicle, the shaft 116 is driven, by the forward momentum of the vehicle, to rotate in the forward direction. Because the pressure connections have been reversed on the pump/motor 102, the pump/motor is now resisting the rotation of the shaft 116. As a result, the vehicle is slowed and, at the same time, fluid is drawn from the low-pressure side of the circuit and forced into the high-pressure fluid source 138, the pump/motor 102 functioning as a pump to store energy to be used subsequently. This is commonly referred to as regenerative braking.
If the vehicle is traveling in reverse mode, the sequence of operation will be opposite that previously described. However, the results will remain the same, namely, high-pressure fluid at the port 136 will drive the vehicle in reverse, while reversing the connection and placing high pressure at port 137 will slow the vehicle as it travels in reverse.
A pump/motor and its operation are described in much greater detail in U.S. patent application Ser. No. 10/379,992, entitled HIGH-EFFICIENCY, LARGE ANGLE, VARIABLE DISPLACEMENT HYDRAULIC PUMP/MOTOR, which is incorporated herein by reference, in its entirety. This application will provide additional background on the features and operation of a bent-axis pump/motor.